Apparatus for treating material



Sept. 20, 1938. B. M. CARTER I APPARATUS FOR TREATING MATERIAL original-Fil ed Jan. 3, 1933 2 Sheets-Sheet l \o INVENTOR ,3. M far/er 70ATTORNEY Sept. 20, 1938.

B. M. CARTER APPARATUS FOR TREATING MATERIAL Original Filed Jan. 3, 19332 Sheets-Sheet 2 INVENTOR B. M. C'ar/er *7 ATTORNEY Patented Sept. 20,1938 UNITED STATES PATENT OFFICE 2,130,731 APPARATUS ron TREATINGMATERIAL Bernard M. Garter, Montclair, N. 1., asslgnor to GeneralChemical Company, New York, N. Y., a corporation of New York Originalapplication January s, 1933, Serial No. 649,786. Divided and thisapplication April 28, 1937, Serial No. 139,478

K 9 Claims. (01. 34-4) primarily directed to rotary drum or. cylinderdrying apparatus. Drying material in such apparatus has been heretoforeproposed In prior operations, it has been customary to continuously passthe material to be .dried through an'elongated rotary drum against acountercurrent flow oi. heated drying medium such as air. Because of thelow melting point of the salts or similar materials being dried, it isnecessary in practical operations that the highest temperature of thedrying air be relatively low, i. e., considerably less than thesoftening point of the material. In countercurrent drying, the nature ofthe operation is such that the temperatureof the heated drying air isgreatest at the air inlet-salt outlet end of the drying zone or chamber.The temperature of the heated drying air decreases as the air currentpasses through the drying zone, and is at a minimum at the point wherethe air leaves the salt inlet-air outlet end of the drying zone. Hence,the moisture-carryingcapacity oi the air current is at a minimum as theair stream leaves the drying chamber. moisture-carrying capacity of theair as it is discharged from the drier, together with other factors,limits the production of dry material by a single unit of apparatus.

The invention aims principally to provide apparatus for drying salts andsimilar materials of such construction that the output of a unit ofgiven size may be largely increased. A further understanding of theobjects and advantages of the invention may be had from a considerationof the following description taken in connection with the accompanyingdrawlngaln which Fig. 1 is a vertical, longitudinal section of one endof the dryer, showing in elevation an axially Fig. 4 is a transversesection on line 4-4 of- Fig. 3;

Fig. 5 is a transverse section on' theline 55 01. Fig. 3;

Accordingly, the

Fig. '6 is a transverse section on line 6-6 of Fig. 1;

Fig. 7 is a'similar transverse section on line 1-1 of Fig. 1;

Fig. 8 is an enlarged view, partly in section, of 5 that portion of thegas distributing pipe between sections M and 5-6, Fig. 3;

Fig. 9 isa transverse section on line Fig- H of Fig. 10 is a-developedplan of a damper in the 10 gas distributing pipe;

Fig. 11 is an end elevation of the damper taken on the line ll-ll'ofFig. 10;

Fig. 12 shows temperature curves, the purpose of which will behereinafter noted, and 15 Fig. 13 is an elevation taken approximately onthe line Iii-l3 of Fig. 1.

Referring to Fig. 1 of the drawings, the reference numeral 5 indicatesone end of a cylindrical drum providing a drying chamber 6. The drumcarries several longitudinally spaced, circumferential tires 1 restingin supporting rollers 8. The end of the drier, not shown, has mountedthereon an annular gear meshing with a drive pinion through which thedrum is rotated from a source of power. The salt outlet end 9 of thedrum pro- Jects into a flxed housing 10 into the bottom of whichmaterial is continuously discharged from the drum. One vertical sidewall of the housing I I0 has attached thereto a circular flange llengaging'a flange I2 carried by the tire I, flanges H and I2 forming asubstantially gas-tight joint laden air from the apparatus; Such fixedhous- 40 ing is also equipped with conventional means for continuouslyfeeding "material into the salt inlet end 01 the rotary drum. As iscustomary in ape paratus of this type, the salt inlet end of thecylinder is elevated slightly to facilitate movement of, materialgradually toward the salt discharge end in fixed housing ill. The drumis rotated in the direction of the arrow 15 in Fig. 6. Reference numeralI, Figs. 1 and 2, indicates a blower, driven by motor ii, the pressureside or the blower'being connected through conduit l8 and opening I!with the interior of housing III.

In operation, drying medium, such as heated air, is fed into the-saltdischarge end 9 of the drum from the housing Ill, passes through drying5 chamber 5 countercurrent to the direction of movement of the salt, andflows from the salt inlet end of the drum into a fixed housing similarto housing ill, from which the air is eventually discharged to theatmosphere.

As shown in Figs. 1' and 7, projecting from the inner face of thecylinder 5 are longitudinal angle irons 20 to which are attachedserrated staggered relation, near the salt discharge end are baflies orgrilles 23, 24 and 25 shown in side and end elevations in Figs. '1 and 7respectively. The baflies are-screen-like frames, connected atlongitudinal edges 26 and 21 with adjacent serrated plates 2l. Thebaflies prevent lumps from passing through with dry salt, and effects.more thorough cascading of fine, nearly dried material than is securedby the serrated angles. At these grilles, the nearly dry salt iseffectively showered through the drying atmosphere in a manner whichcould not be eflected at the opposite end of the kiln where the salt iswet.

Additional quantities of heated drying medium are fed. into the drumthrough an axially disposed, longitudinal distributing pipe 30 shown inelevation in Fig. 1, and in enlarged section in Fig. 3. The inlet end ofpipe 30 iwfixedly supported at 3i in outer side wall 32 of the housingi0. Pipe 30 is cylindrical from wall 32 to section 5-5 in Fig. 3. Fromthis point, pipe 30 tapers uniformly toward the small end 33, which isclosed off by a circular disk 34. Rigidly connected to and extendingthrough disk 34 is a stub shaft 35, the outer end of which passesthrough a bearing 35 supported by a spider, the

arms 31 of which are riveted at the outer ends to angle irons 20 and atthe inner ends to the circularv flange 38 of thebearing 36. Hence, the

small end of the fixed pipe 30 is maintained in position by hearing 35.The gaseous drying medium, such as air, is fed into pipe 30 from aninlet conduit 40. The top side of pipe 30 may advantageously be coveredwith insulating material, such as asbestos, to prevent overheating andpossible melting of salt material falling on top of the pipe duringrotation of the drum- The tapered portion 4i of the air pipe 30, betweentransverse sections 4-4 and 5-5, is provided on the lower side with aplurality of elongated openings 45, 46, 41, 40, 49, and 50 of uniformlength and width. The openings are separated by the shortsections 5ileft uncut to avoid weakening of the pipe. In effect, all of theopenings together. may be considered as constituting,

' a single elongated slotin the underside of tapered section 4|. Asnoted, the drum rotates in the direction of the arrow i5 in Fig. 6,andaccordingly theshell, in conjunction with angles 20 and plates 2|,tends to carry material upwardly through the left half 53 (Fig. 6) ofdry-.

ing chamber 5. In order to cause air entering the drying chamber 6through openings -50 to be directed toward thesalt ibeing dried, thelongitudinal center line of openings 45-50 is displacedcircumferentially from the vertical a distance equal to an angle A asindicated particularly in Fig. 8, and also'in Figs. 4"and 5.

Angle A may for example be about 20. The openings are therefore oil thevertical center in the direction of rotation of the cylinder so that thehot air is directed toward the surface of the bed of salt at a point atwhich the bed is of substantial depth.

The passage of air through openings 45-50 is controlled by an eccentricdamper indicated generally by reference numeral 50, and shown in Fig. 10in plan. In Fig. 10, the damper is curved upwardly out of the plane ofthe paper as will be seen from Fig. 11. The curvature of the damper issuch that the convex surface conforms with the inner surface of taperedsection 4i of the air pipe 30. The damper is rigidly connected throughhangers 5| to a longitudinally extending pipe 52, the inner end 53 ofwhich fits over and may oscillate about the inner end of fixed stubshaft 35. The opposite end of pipe 62 is rotatably supported in a fixedbearing 55 shown in Figs. 1 and 3. Keyed to the outer end of pipe 62 isan operating handle 65 (Fig. 13) and since the inner end of the pipe isrotatably carried by stub shaft 35 andthe outer end of the pipe isrotatably supported in bearing 55, the position of the damper 60relative to the openings 45-50 may be controlled by manipulation ofhandle 65.

Referring to Fig. 10, line 63 represents the center line or crest of thedamper. When the latter is positioned to close all openings 45-50, asshown in the large section Fig. 8, line 53 coincides with thelongitudinal center of openings 45-50 indicated by the dotted linebetween points B and C (Fig. 8). In the particular damper illustrated,although specific dimensions are immaterial, dimension .D (Fig. 10) isslightly posed in different angular relation with respect to center line58, that is, the taper of edge I2 with respect to line 58 is sharperthan the taper of edge I3 with respect to center line 05. When thedamper is in place in pipe 30 and adjusted so that all openings 45-50are closed, longitudinal edges 12 and 13 and transverse edgesrepresented by dimensions D, F, E, and G oc-, cupy the positions shownin Fig. 8.-

The gas distributing pipe 30 is also provided at I5 (Fig. 1) with aplurality of openings 15 shown in section in Fig. 9. Openings I5 are tothe right of thevertical (Fig. 9) and are arranged similarly to,openings 45-50 so that hot gas entering the drum through openings isdirected into the body of salt beingvcarried up wardly in the'directionof the arrow ii of Fig.

6. Openings 10 are controlled by a longitudinally sliding damper I8(Fig. 3) comprising a ring 19 carried by spider arms 30, the inner endsof which are connected to a sliding sleeve ll extending outwardlythrough bearing (Fig. 1).

Attached to the outer end of sleeve 0| is a lug 84 (Fig. 3) to which isplvotally connected at 35 an operating handle 05 one end of which is,,pivoted at 31 to the end of a link 30 pivoted to a fixed bracket 30,shown more clearly ln-Fig. 1.

The invention may be employed in practicesubstantially as follows:

As noted, the invention is directed particularly softening orliquefaction at relatively low temperatures, and hence should be driedat temperatures below-the softening point. For convenience and by way ofillustration, the operation of apparatus of the invention will bedescribed in connection with the drying of trisodium phosphate, a saltcontaining considerable quantity of however, that the apparatus of theinvention is applicable for use not only to the drying of salts dryingor treatmentof any material from which water or other vaporousconstituents must be evaporated at temperatures below that at which Iliquefaction or incipient fusion of the material treated would takeplace.

In customary commercial practice, trisodium phosphate crystals,containing 12 molecules of water, are first separated from the motherliquor by means of a filter, and may bc'washed with I water to removemother liquor ordinarily retained by the dewatered crystals. Forexample, after gal filterdelivers a product containing from to 8% freewater. Initial dewatering of the crystal slurry and the apparatusemployed constitute no part of this invention.

To meet certain trade requirements on trisodium phosphate crystals, forexample, all free water and a small amount of the water ofcrystallization must be removed from the centrifuged equivalent of notless than about 101.5% of Na3PO4.12H2O and such water is removed byexposure of the wet salt to a heated gaseous drying medium such as hotair. Heretofore, drying has been accomplished in operations .involvingcounter-current flow of salt and hot air through a rotary drum, the hotair initially introduced into the drier at the salt discharge end beingheated to thedesired temperatures by any convenient means. In suchoperations, involving countercurrent flow of salt and drying the amountof salt which may be dried in any given apparatus is dependent upon thediiference in water content between the air entering the salt outlet endand leaving the salt inlet end-of the per unit of time is more or lessdependent upon in summer than in winter on account of the highertemperature and the humidity of the atmosphere in warm weather. a

The basic features of the process aspects of the invention may be moreclearly understood from a brief consideration ofsome of the fundamentalprinciples involved. In summer in the temperate zone, temperatures ofabout 80 F. and relative humidity of about 70% frequently prevail. Underthese conditions, atmospheric air contains about 7.6 grains of water percubic foot.

On heatingathe volume increases, and the moison heating.to 100F.,contains about 7.4 grains of water per cubic foot, and has a relativehumidity of about 38%. On further heating to, say, 120 F., such air, asintroduced into the salt outlet end of the drier, would contain about7.1 grains ofwater per cubic foot'and the relative v humidity decreasesto about 21%. Since in practical-operation, complete equilibrium is notobto apparatus for drying material subject to water of crystallization.It is to be understood,

5 containing water of crystallization', but to the.

the water wash, one well-known type of 'centrifu by refrigeration,drying, etc.

salt so that the dried product will contain. the

drier. Furthermore, the output of such a drier atmospheric conditions,the capacity being lessture carrying capacity is raised so-that such airtained, the humidity of the heated air discharged from the salt inletend ofthe drier decreases as the temperature increases. Thus, airleaving the salt inlet end of the drier at about 100 F. and relativehumidity of about 60% would carry about 11.6 grains of water per cubicfoot, or about 4.2 grains per cubic foot in excess of enteringatmospheric air heated to about 100 F., having a relative humidity ofabout 38% and containing about 7.4 grains of water per cubic foot.Further, air leaving the salt inlet end of the drier at about 120 F. anda relative humidity of about 50% would carry about 17.2 grains of waterper cubic foot, or about 10.1 grains per cubic oot in excess of enteringatmospheric air heated to about 120 F.', having a relative humidity ofabout 21% and containing about 7.1 grains of water per cubic foot.Accordingly, a given volume of air leaving the drier at about 120 F. andabout 50% relative humidity would dry more than twice the amount. of.wet salt that would be dried by the same amount of air leaving the drierat about 100) F. and about 60% relative humidity.

It will be understood the output per unit of time of a drier' of a givensize is determined by quantity of airv employed, moisture content ofsuch air, and the temperature to which-the air is heated prior tointroduction to the drier. The initial moisture content of the air isdetermined by atmospheric conditions, and is not subject to control,unless the air is previously conditioned The remaining two controllablefactors are also subject to limitation. The volume of drying airemployed cannot be in excess of that at which it would tend to carry thematerial out of the drier in suspension, and on the other hand, thetemperature of the drying air cannot be raised above that at which thematerials being treated would bedeleteriously affected. a

In the present description of the operation of the process, it is to beunderstood the reference to specific temperatures, volumes of dryingair,and dimensions of the drier are illustrative; and

are mentioned only to facilitate description of .one embodiment of theinvention.

140 F. without creating a sticky condition that Produces undesirablecaking. Thus, in practice it is not desirable to allow the maximumtemperature of the drying air to exceed about 135 F. In prior practice,it has been customary to pass the salt continuously through a rotarydrum in contact with a stream of air flowing countercurrent through thedrier, the temperature of the drying being about 135 F.

It has been found'that in prior practice, e. g. where wet salt anddrying air pass countercurrent through thedrier, the temperature of thedrying air drops of! rapidly, in the first onethird of the length of thedrying chamber, and thereafter remains substantially constant until theair leaves the salt inlet end of the drier. In Fig.12, the "abscissarepresents the length of the the temperature of the drying air. Dottedcurve K approximately indicates the temperatureconditions existing inthe drierwhen operated in accordancewith prior practice; From thiscurve, it will be. seen that while passing through approximately thefirst third of the drier, the temperature drops from approximately 135F. to say air introduced intothe salt outlet end of the drier dryingchamber 6, and the ordinate represents about 110-l12 F., and thereafter,during the subsequent two-thirds of passage through the drier, thetemperature of the drying air decreases gradually to about 100 F., atwhich temperature the drying air passes out of contact with the wet saltbeing fed into the salt inlet end of the drier.

In accordance with the present invention, operations are conducted sothat the temperature of the drying air leaving the drierisconsiderablyraised, thus largely increasing the water carrying capacity of thedrying air at the time of last contact with wet salt. By means of thepresent method and apparatus, conditions in the drying chamber may be socontrolled that the temperature of the air leaving thedrier may beregulated as desired within certain limits. From a consideration of thetemperature curve K of Fig. 12, it will be seen that if properlyregulated quantities a of drying gas, heated to proper temperatures, are

introduced into the drier beginning at points beyond approximately thefirst third of the drier (measuring from the salt outlet end), thetemperature of the drying atmosphere in the subsequent two-thirds ofthedrying chamber may be raised, and the water carrying capacity of thedrying air, as discharged from the salt inlet end of the drier, largelyincreased. In the present invention, such temperature control in thedrier may be had by introducing heated gas into the drying chamber 5through the gas, distributing pipe 30, by suitable regulation ofdampersv 50 and I5.

In the apparatus illustrated, it may be assumed for example, drum 5 isabout feet long. The

taper of pipe 30 begins at section 5-5, Fig. 3,

about '7 feet from the salt outlet end 9 of the drum, and at a pointwhich is indicated by a corresponding line 5-5 on Fig. 12. As thetemperature of the drying air has dropped materially at about line 5-5(Fig. 12), to accomplish the purposes of the invention, controlledquantities of *air heated to proper temperatures are introduced into thedrying chamber through one or more of the openings -50 of pipe 30. It isnoted, section line 4-4 (Fig. 3), corresponds approximately with line4-4 on Fig. 12. The particular portion of the drier, between lines 5-5and 4-4 (Fig. 12) into which hot gas from pipe 30 is introduced isselected by manipulation of the damper 50.

I In Fig. 8, the damper is shown in such position that all openings45-50 are closed. It will be recalled fromthe foregoing description thatedges I2 and 13 are pitched oppositely and at different angles withrespect to center line 58 of damper 0.

Referring to Fig. 8, it will be seen that movement of damper in thedirection of the arrow 95, first uncovers a portion or the whole ofopening 45 nearest the small end of tapered section 4|. Thus, acomparatively short downward movement of handle (Fig. 13) uncovers theopening 45, and admits heated air from the pipe 50 into the interior ofthe drum at the point at which opening 45 is positioned. Because of therelatively sharp pitch of edge I2, with respect to center line 58 of thedamper 50, it will be seen that continued movement of damper 50 inthe'direction of the arrow 55 successively uncovers, openings 45-50 inthe order named, until when the handle 55 is in the position of thedotted line 55 (Fig. 13), all openings 45-50 are uncovered, and becauseof the taper of pipe 30 substantially qual quantitles of air pass"through each opening into the drum. Thus, when it is desired tointroduce air as noted above where the damper was fully of the taperedsection, and then progressively to- In one particular series of tests,carried out in to temperatures of about 400F. was fed into the than saltoutlet end 5, handle 55 is moved downwardly, and as many 0! the openingsas necessary may be uncovered, and additional hot gas admitted toselected portions of the drum.

In other situations arising in practice, it may desirable to introduceadditionalhot gas only or I initially in portions of the drying chambernearer the salt discharge end of the drum. This may be accomplished byraising handle 55 which ,causes movement of damper 50 in the directionof1 the arrow 91 in Fig. 8. As'edge E of the damper is shorter thanedge F,it will be seen that such movement of the damper first uncovers theopening 50 adjacent the section-line 5-5 of Fig. 3. On account of thepitch of edge 13, with respect 1 to center line 58 of damper 50, furthermovement of the damper in the direction of the arrow 51 uncovers opening50-45 progressively in the order named. When handle 55 is in theposition of dotted line 59, all openings are uncovered, and air entersdrying chamber 5 in the same manner opened by downward movement ofhandle 55.

Thus, by moving handle 55 downwardly, air is introduced into the drierfirst at the small end ward the larger section, if downward movement ofhandle 55 is continued. On the other hand by lifting handle 55, air isintroduced into the drum first through the opening 50 adjacent sectionhne 5-5 of Fig. 3, and thereafter, on further upward movement of handle55, through openings progressively nearer the small end of adistributing pipe 30. Accordingly, by adjustment of the position of thedamper to suit spe- ClfiC operating conditions, additional quantities ofhot drying gas may be introduced into any portron of the drying chamber,and the temperature conditions therein controlled as required. It willbe seen that by reasm of the difference of pitch of edges '|2 and 13with respect to center line 55 of the damper, all the openings 50-45 maybe more rapidly opened or closed by raising handle 55 or lowering thesame to the horizontal positron, thus in effect using edge-I3 as theworking" edge of the damper. On the other hand, downward movement ofhandle 55 and raising the same to the horizontal position makes edge I!the working edge, and as the pitch of edge I! is sharper, with respectto center line 58, the openings 45-50 are uncovered or covered at a lessrapid rate. In practice, it has been found generally desirable to admitadditional hot drying gas nearer the salt inlet end, say throughopenings 45, 45 and 41, rather than near the salt outlet end. Thus,handle 55 is manipulated so that edge 12 is employed as the workindamper. g edge of the midsummer over an extended period of time, and atan average atmospheric temperature of about F. and about 10% relativehumidity, operations were conducted so that approximately 40 tons ofdried trisodium phosphate were produced by the drier in 24 hours, about10.8% free and combined water having been removed from the wet salt. Thetotal quantity of drying medium employed was about 5,000 cubicfeet perminute. About half this volume of air, at temperatures about 131 'F.,was fed into the drier from the fixed housing l0. An equalvolumejconsisting of products of combustion from an oil' burner, heateddistributing pipe 50 from pipe 40, and introduced into the drier withall the openings 45 -50 uncovered. The combined volume of gas left thedrier at temperatures of about 122 F., the temperature prevailing in thedrum being indicated approximately by the curve L, in Fig. 12. In theabovetests, the followlng results were obtained:

Food Product Percent Percent Na;PO .12H,0 92. 96 103. 04 NaOH l. 60 1.25 Na|C0,. .78 1.21

By proceeding in accordance with the above,

the output of the drier was approximately doubled over operationscarried out in a drier of the same size, but built and operated as inthe prior practice. It will be seen from Fig. 12, the temperature of thedrying medium leaving the drier is about 20 higher than previouslyobtainable,

thus eiTecting the largely increased capacity of the drier.

By operation of damper I8 controlling openings 16 positioned relativelynear the salt disfrom the housing l may be at temperatures of about 100F., thus cooling the dried salts, to some extent, just prior todischarge from the drier, such cooling advantageously. permittingpackaging of the product without caking', and without the use ofadditional equipment to cool the product prior to packaging.

Where air or other gaseous heating medium is introduced into the dryingchamber from house ing l0 at lower temperatures of about,"say, 100 F.,the temperature in the drying chamber just beyond the salt outlet end 9may be rapidly raised to the desired maximum temperature by opening thedamper 18, and. permitting admission of hot gases through openings I6.By this operation in conjunction with manipulation of damper 88, atemperature curve in the drier approximating curve M may benobtained,which curve, as will be seen, converges with curve L at a point near thesalt outlet end of the drier, the temperatures thereafter approximatingthose which prevail in instances where the drying air is initiallyintroduced at 131-132' F. I

In the above specific example, it will be noted the hot combustionproducts entering the drier through pipe 30 were heated to temperaturesof about 400 F. No particular temperatures for the high temperature gassupply need be employed. Improved results, over prior practice, may beobtained where the hot gases entering through pipe 80 are at anytemperature above that of the gas entering the drier from housing I 0.The higher thetemperature of the gases entering the drier from pipe 30,the higher the temperature of the combined gas stream leaving the saltinlet end of the drier, and accordingly the greater the output of thedrier and the emciency of the dryingoperation. To obtain substantiallyimproved in- -crease in the drier capacity, the temperature of the gasintroduced through pipe 30 should not be less than about, say, 250 F.The upper limit of the temperature of the gas from pipe 30 is'controlled by the nature of the material being treated.

enough to raise the temperature of the combined gas stream in the driersufficient to cause softening or injury to the material being treated.The volume of the combined gas stream in the drier should not be inexcess of that at which material would be carried away in suspension. i

It will also be understood any suitable gas may be used for both thehigh and low temperature supply. Air heated by heat exchange may beemployed for either or both low and high temperature supply, and alsocombustion gases, if sootless, may be utilized for either or both thelow andhigh temperature supply, thus eliminating use of steam heaterspreviously employed, and thereby eil'ecting economies in cost of heatsupplied to the drier.

I claim:

1. Apparatus for treating material comprising a rotary drum forming atreating chamber, means for introducing solid material to betreated-into one end of the chamber, means for moving the materialthrough the chamber, means for introducing a primary stream of gas intothe opposite end of the chamber, means'for passing the gas streamthrough the chamber countercurrent to the movement of the solidmaterial, a fixed'conduit projecting into the chamber from said oppositeend and terminating in a tapered section extending longitudinallythrough a substantial part of the chamber, an elongated slot in theunderside of and extending substantially the lengthof the taperedsection of the conduit, a damper in the conduit for closing the slot,said damper having oppositely pitched edges so formed as to close off,on movement of the damper, the whole of the slot or variable portions ofeither end of the slot, a

second opening in the conduit adjacent said oppo 3. Apparatus fortreating material comprising,

a rotary drum forming a treating chamber, means for introducing solidmaterial to be treated into one end of thechamber, means for moving thematerial through the chamber, means for introducing a primary stream ofgas into the opposite end of the chamber, means for passing the gasstream through the chamber countercurrent to the movement of the solidmaterial, a fixed con-,

duit projecting into the chamber from said opposite end and terminatingin a tapered section extending longitudinally through a substantial partof the chamber, an elongated slot in the underside of and extendingsubstantiallythe length of the tapered section of the conduit, a damperin the conduit for closing the slot, said damper having oppositelypitched edges so formed as to close off, on movement of the damper, thewhole of the slot or variable portions of either end of the slot.

, 4. Apparatus for treating material comprising a chamber, means forintroducing materia to be treated into the chamber, a conduit in thechamber for introducing treating medium, an opening in the conduit and adamper associated with the opening, said damper having opposite edgesdisposed at different angular relation with respect to the interveningcenter line of the damper and so formed as to close oil? on movement ofthe damper the whole of the opening or variable portions of either endof the opening.

5. Apparatus for treating material comprising a chamber, means forintroducing material to be treated into the chamber, a conduit in thechamber for introducing treating medium, an opening in the conduit and adamper associated with the opening, said damper having oppositeconverging edges so formed as to close off on movement of the damper thewhole of the opening or variable portions of either end of the open ing.

6. Apparatus for treating materials comprising a chamber, means forintroducing material to be treated into the chamber, a conduit in thechamber for introducing treating medium, an opening in the conduit and adamper associated with the opening, said damper having oppositelypitched edges so formed as to close off on movement of the damper the-whole of the opening or variable .portions of either end of theopening.

said damper having oppositely pitched edges so, formed as to close ofion movement of the damp er the whole of the opening or variable portionsof either end of theopening.

8. Apparatus v for treating material comprising opening.

a chamber, means for introducing solid material to be treated into oneend 01' the chamber,

means for moving the material through the chamber, means for introducinga primary stream of treating medium into the opposite end of thechamber, means for passing said primary stream through the chambercountercurrent to the movement of the solid material, a conduitprojecting into the chamber for introducing further quantities oftreating medium, said conduit extending longitudinally through asubstantial part of the chamber, an elongated opening in the conduit anda damper associated with the opening,said damperhaving oppositelypitched edges so formed as to close 011 on movement of the damper thewhole of the opening or a variable portion of either end of the opening.a

9. Apparatus for treating material comprising a rotary drum forming atreating chamber,-

means for introducing solid material to be treated into one end of thechamber, means for moving the material through the chamber, means forintroducing a primary stream of gas into the opposite end of thechamber, means for passing the gas stream through the chambercountercurrent to the movement of the solid material, a conduitprojecting into the chamber from said opposite end for introducingfurther quantities of treating medium, said conduit terminating in atapered section extending longitudinally through a substantial part ofthe chamber, an opening in the tapered section of the conduit and adamper associated with the opening, said damper having oppositelypitched edges so formed as to close oif on movement of the damper, thewhole of the opening or a variable portion of either end of the BERNARDM. CARTER.

